add subsecond support to Now() (#242)

Author: maikhanhbui

mssql/functions.py

@@ -10,6 +10,7 @@
 from django.db.models.expressions import Case, Exists, Expression, OrderBy, When, Window
 from django.db.models.fields import BinaryField, Field
 from django.db.models.functions import Cast, NthValue, MD5, SHA1, SHA224, SHA256, SHA384, SHA512
+from django.db.models.functions.datetime import Now
 from django.db.models.functions.math import ATan2, Ln, Log, Mod, Round, Degrees, Radians, Power
 from django.db.models.functions.text import Replace
 from django.db.models.lookups import In, Lookup
@@ -123,6 +124,10 @@ def sqlserver_exists(self, compiler, connection, template=None, **extra_context)
     sql = 'CASE WHEN {} THEN 1 ELSE 0 END'.format(sql)
     return sql, params
 
+def sqlserver_now(self, compiler, connection, **extra_context):
+        return self.as_sql(
+            compiler, connection, template="SYSDATETIME()", **extra_context
+        )
 
 def sqlserver_lookup(self, compiler, connection):
     # MSSQL doesn't allow EXISTS() to be compared to another expression
@@ -456,6 +461,7 @@ def sqlserver_sha512(self, compiler, connection, **extra_context):
 Round.as_microsoft = sqlserver_round
 Window.as_microsoft = sqlserver_window
 Replace.as_microsoft = sqlserver_replace
+Now.as_microsoft = sqlserver_now
 MD5.as_microsoft = sqlserver_md5
 SHA1.as_microsoft = sqlserver_sha1
 SHA224.as_microsoft = sqlserver_sha224